Table 1. Comparisons of Baseline Characteristics of Patients With Rectal Cancer by Treatment Modality.
| Characteristic | No. (%) | P value | |
|---|---|---|---|
| Radiotherapy (n = 5310) | No radiotherapy (n = 14 832) | ||
| Age at rectal cancer diagnosis, median (IQR), y | 61 (52-70) | 66 (56-75) | <.001a |
| Age at rectal cancer diagnosis, y | |||
| 20-49 | 1047 (19.7) | 1767 (12) | <.001b |
| 50-69 | 2886 (54.4) | 7230 (48.7) | |
| ≥70 | 1377 (25.9) | 5835 (39.3) | |
| Year of rectal cancer diagnosis, median (IQR) | 1999 (1991-2006) | 1993 (1984-2002) | <.001a |
| Year of rectal cancer diagnosis | |||
| 1975-1984 | 503 (9.5) | 4095 (27.6) | <.001b |
| 1985-1994 | 1228 (23.1) | 4063 (27.4) | |
| 1995-2004 | 1984 (37.4) | 3983 (26.9) | |
| ≥2005 | 1595 (30) | 2691 (18.1) | |
| Race | |||
| White | 4449 (83.8) | 12 353 (83.3) | <.001b |
| Black | 352 (6.6) | 1170 (7.9) | |
| Otherc | 509 (9.6) | 1309 (8.8) | |
| Tumor grade | |||
| Grade I/II | 3992 (75.2) | 9899 (66.7) | <.001b |
| Grade III/IV | 777 (14.6) | 1141 (7.7) | |
| Unknown | 541 (10.2) | 3792 (25.6) | |
| Tumor stage | <.001b | ||
| Localized | 1742 (32.8) | 11 393 (76.8) | |
| Regional | 3568 (67.2) | 3439 (23.2) | |
| Tumor histology | |||
| Adenocarcinoma | 4831 (91) | 14 181 (95.6) | <.001b |
| Mucous tumor | 360 (6.8) | 490 (3.3) | |
| Other | 119 (2.2) | 161 (1.1) | |
| Tumor size, cm | |||
| <2 | 191 (3.6) | 827 (5.6) | <.001b |
| ≥2 | 1306 (24.6) | 1323 (8.9) | |
| Unknown | 3813 (71.8) | 12 682 (85.5) | |
| Chemotherapy | |||
| No | 1293 (24.4) | 13 892 (93.7) | <.001b |
| Yes | 4017 (75.6) | 940 (6.3) | |
| Follow-up time of patients with rectal cancer, mo, median (IQR) | 120.5 (93-175) | 154 (99-232) | <.001a |
| Total person-years at risk | 65 397 | 205 487 | |
| Latency between rectal cancer and SGMN, mo, median (IQR) | 110 (69.3-156.5) | 123.5 (63.3-137.8) | <.001a |
| Patients who developed SGMN | 144 (2.7) | 176 (1.2) | <.001b |
Abbreviations: IQR, interquartile range; SGMN, second gynecological malignant neoplasm.
a
P values were calculated using the Mann-Whitney test for continuous variables and χ2 test.
b
P values were calculated using the Mann-Whitney test for categorical variables.
c
Other includes American Indian/Alaska Native and Asian/Pacific Islander.